This 107-year-old British doctor is friends with the queen, treated Saddam Hussein and is still working

At 107-years-old, Dr. William Frankland is the world's oldest practicing doctor. Renowned in medicine as the "Grandfather of Allergy" and once the doctor of Saddam Hussein, London-based Frankland continues to consult several patients around the world.

But what's the secret behind his longevity?

"I don't smoke, and I don't overeat," Dr. Frankland explained.

Watch this episode of "Lifers" in the video above.